Wifi Calling and 4G Calling

[tarantella]

What is the up-to-date situation on WiFi Calling and 4g Calling please, specifically in relation to iphones and Android devices NOT purchased from Three.

There are lots of conflicting bits of information floating around.

Will all new devices bought in 2023 now have Wifi Calling and 4g Calling fully enabled, or will there still be any restrictions or caveats?

I would really appreciate a full and comprehensive answer from one of the Moderators please: thanking you very much in advance.

[PeppaSC]

4g calling does work on the three network for my phone. It doesn't show VoLTE at the top of the screen like EE does, but signal doesn't drop from 4g when on the phone. My husband is with an O2 provider and when he's on the phone his data signal drops to an H which is absolutely ridiculous. Definitely an EE or three network for me while I have this phone. 

[sc1999]

My S21FE only shows wifi calling when I have a poor 4g, or 3g, signal. This applies to 3 and Vodafone as I have 2 sims in my phone. That said I have recollections that there are sometimes issues with phones not supplied by 3 or with EU and not UK firmware.